At can be very handy to automatically add a timestamp to a Tomboy note but the feature is not enabled right out of the box. Fortunately it is very easy to turn on this feature.
Open Tomboy Preferences, click on the Add-ins tab, and select the Tools Add-in dropdown list. Select Insert Timestamp and click on the Enable button to the right.
You can also change the default timestamp format or create your own by clicking the Preferences button.
Now simply press Ctrl+d while typing a note and a timestamp will be inserted at the curser.